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tt'd -i 




W ' 1 4 1934 







HOW 



TO 



CURE CONCRETE 



A Manual of Instruction on th 

Cunt) of Concrete 



■ 














T H E 



DOW CHEMICAL 



CO Pan 



MIDLAND, MICHIGAN 

S«co*d and Mar »\ 

I 



^-V 



PATCNTCC' FtftbuAwv it iV2 



DOWFLAKE 

L_ft CALCIUM CnLOKiOC 




Copyright J 033 



The Dow Chemical Company, Midland, Micki* 



K"n 



FOREWORD 

This manual is published to pro- 
vide important facts selected from 
reports of the Highway Researcli 
Board, The U. S. Bureau of Public 
Roa<l>, various state highway depart- 
ments, and other reliable sources. 

We have collected definite and reli- 
able information and have put it in 
brief form as a safe, handy guide to 
concrete curing practice. 

We also have for distribution two 
other manuals of interest to highway 
officials and workers: 

How to Maintain Roads. 



How to Control Dust. 



Litl 



I 



had I 



w nhnjr 



ler may ne naa i>\ 

The Dow Chemical Company or il> 
branch offices. 




HOW TO CU"E CONCRETE 



CURING CONCRETE PAVEMENTS 

"Proper curing of concrete is the setting up of favorable 
conditions for chemical action during the earlv hardening 
period" (Report of Highway Research Board Curing Commit- 
tee). In setting up these favorable conditions the presence of 
sufficient moisture to insure complete hydration of the cement 
is important. The use of calcium chloride, either applied on 
the surface, or incorporated in the mix, provides thi> moisture 
and insures maximum strength concrete. 

The study by the Highway Research Board Curing Com- 
mittee of the results of investigations conducted bv many States 
and the Bureau of Public Roads, as well as the condition of 
thousands of miles of calcium chloride cured concrete pave- 
ments has proven that the use of calcium chloride surface, or 
integral curing, provides maximum strength and durability 
uniformly throughout the pavement slab at a maximum of 
tune and at a reasonable cost. 

The more scientific testing is done, the more results point 
to the use of Dowmike calcium chloride as meeting all require- 
ments for durable concrete, controlled action and cost, for 

earl> ivement use and quick release of costly equipment. 

An Added Control Factor — An Added Safeguard 

Dowflake calcium chloride provides needed control com- 
parable to that which now governs the ingredients and pro- 
portions of the mix, because its analysis is exact, its reactions 
• •an be accurately planned in comparison with dirt and water 
methods taken as standard. 

Conceded as satisfactory and rated as standard, dirt and 
water still offer variables. In contrast calcium chloride gives 
more exact control — is an inUhd safeguard. 

Who. for instance, knows the exact thickness and weight 
ot earth' Does every square yard of dirt-cure have the same 
thickness I Or the same amount of water? Or any water? 
1> inspection possible, thorough, and constant? 



page: -4 




HOW TO CURE CONCRETE 



r 

r- 



II, with all these uncertainties, dirt and water is standard, 
then js it not a fact that a material of known action, performing 
the same functions with le>s labor and less liabilih of losing 
moisture, will be the accepted method everywhere? 

Calcium chloride is the favored method for its exactness, 
for its automatic control. Calcium chloride gives a positive 
cure. Once applied, it does its work whether continually 
inspected or not. The cost of transporting sufficient calcium 
chloride to cure a mile of slab is but a fraction of the cost of 
providing dirt and water for the same slab. 

If analysis of cement and proportions of mix are vital, 
is it not essential then to have a curing factor as dependable 
and as automatic? 

We have, as advantages of calcium chloride over other 
forms of curing: 

1. Controlled automatic chemical action as exact as the 
chemical action of tested cement. 

2. Saving most of the cost of getting curing materials to 
the job — and all cost of removing them. 

3. Acceleration of curing action where time is a factor. 

4. Additional cold weather protection when normal pre- 
cautions are observed. 




Concrete curing with Douflake is automatic, accurate and fast 



PAGE 5 



HOW TO CURE CONCRETE 



ADVANTAGES TO CONTRACTORS AND 

OFFICIALS 



I improved properties would, of course, 
be sufficient "reason for the use of Dow flake calcium chloride 



Showing a slab o 



.i-a curing agent. 



Yet if there were no advantages to the slab 



except merely a maintenance of standard values, calcium 
chloride would Mill be a boon to contractors and officials. 



Saves Hauling and Disposing of Dirt 

There are places, of course, where dirt, water and straw 
are right at hand in quantities, so that curing costs may be no 
higher than with calcium chloride. But there is a question 
even in such cases if the cost of providing, hauling and dispos- 
ing of dirt and straw is not actually greater. Where dirt is not 
available nearb\ but must be hauled long distances, the balance 
in favor of calcium chloride can mean the difference between 
profit and loss. 

Saies on Pipe Line. Pump Erection and Maintenance 

Dowflake calcium chloride provides its own moisture on 
bring applied direct to the pavement surface alter wet burlap 
has been removed. In case of concrete brought from central 
plants, the use of Dowflake frequently eliminates the need for 
setting up pump and water pipe lines. This saving in itself is 
sizeable, particularly where curing water must be pumped long 
distances. 



Releases Equipment and Man Power 

Instead of maintaining. a crew of men in partial idleness 
to wait for removal of forms, l<> putter about in keeping water 
on the dirt covering, the contractor can release equipment and 
laborers in a much shorter time. The high early strength of 
Dowflake-cured slab permits quicker removal of forms for use 
on new work — avoids tying up unnecessary investment in 
forms, and release^ both men and equipment to speed prog 
on other work, since one man can handle all the curing with 
calcium chloride. 



PAGE fc> 



HOW TO CURE CONCRETE 



Saves on W titer Supply 

Water is frequently scarce. With Dowflake calcium 
chloride curing there's no need to rob the mixer or stop for- 
ward work to use water for curing. Dowflake calcium chloride 
provides its own moisture. Every engineer and every paving 
contractor should make sure to have a supply of Dowflake on 
hand even when curing with dirt and water. There is a critical 
time in curing when the moisture supply must be constant. 
Pumps may break down and wells go dry, yet the pavement 
need not be ruined for lack of curing when Dowflake is avail- 
able. The cost of erecting and maintaining pumps and pipe 
lines, added to the cost of earth hauling and removing, plus 
labor of wetting the dirt continually, if added together will 
show Dow Hake to be as economical as it is fast, sure and safe. 




Dowflake saves heavy expense, especially where earth and water are hard to get 



PAGE 7 



HOW TO CURE CONCRET 



Reduces Curing Labor 

Bv either surface application or as an admixture, curing 
with Dowflake is a part time, one man job as contracted with 
the many men necessary for dirt and water or straw and water 
lie. The decision of "How to Cure" should take into consid- 
eration the investment and wear and tear on trucks to handle 
earth, the labor costs, the shovels and equipment, the super- 
\ ision, the inspection and the hundred and one other items that 
are involved with dirt and water or >traw and water curing. 
Contrast this with wheeling a simple spreader over the pave- 
ment once and you will readily understand why the Dowflake 
method gains fax or so rapidly. 



Makes Inspection Simple and Certain 

Instead of ihe busy job of watching men spread sufficient 
i tih, instead of watching to see that the covering is uniform 
ml is properly welted and kept wet, all the inspector has to 

is to se< that the calcium chloride is applied to the surface 
when ll wet burlap is removed. \o further inspection is 
necessary. One reliable man can assure proper application 
nd positive curing h\ th«' surface application method. When 
used as admixture, the curing operation is assured when the 
concrete is poured. It is automatic and certain. 

// In ( iriirj with (.allium Chloride is Approved by the 

U. S. Bureau of Public Roads 

The Hi»h\\a\ Research Board and the U. S. Bureau of 
Public Roads have done much constructive work in establishing 
eoinp dive values and merits of various curing processes. 
Laboratory test> ha\e been exhaustive. Extensive mileage in 
various states has been cured with calcium chloride and con- 
stant^ checked with other curing processes. The committee 
reports that calcium chloride surface curing (1) doe^ not 
i i<ate \ohime changes that cause checking, (2) doc- not cause 
scaling. (3) attains strengths [uivalent to the wetted earth 
method. < ilcium chloride surface treatment is the only 

method other than wetted dirt which ha- passed all condition- 
set iorth by the Highway R< arch Board as necessary for the 



E e 



HOW TO CURE CONCRETE 



proper curing of concrete. These safeguards plus llie high 
early and permanent strengths derived, fix calcium chloride 
finally and definitely as a superior curing material. This 
means that a contractor gains full approval as well as great 
advantage by using Dowllake calcium chloride. 

Advantages to the Public 

Long time detours are as disappointing to the public as 
they are costlv to the contractor. One cannot always have or 
huild a paved detour. When heavy traffic is diverted for un- 
nesessary periods of time, it causes traffic prohlems that con- 
tinually annoy highway officials because of their annoyance 
to the puhlic. Heavy loads shift. Trucks become mired or 
hreak down and hold up traffic. High early strength from 
calcium chloride curing permits shortening the detour period 
and is, therefore, a public benefit as well as a trouble saver for 
both official and contractor. 

Possibly the public has been spoiled and has learned to 
expect too much. So frequently roads are broken up, graded, 
paved, cured and turned back to traffic so rapidly that the 
public no longer dreads a detour as it did some years back. 
It has learned that modern engineering has taken the annoyance 
out of highway improvement. Nothing aids more in speeding 
up paving operations than rapid curing with calcium chloride. 
Nothing adds more to the profit from a paving operation than 
its quick completion and opening. It is an advantage to the 
puhlic as well as to official or contractor. 



PAGE 9 



HOW TO CURE CONCRETE 




TWO TESTED METHODS 



Calcium chloride curing may be accomplished either by 
the surface application or the admixture method. Both have 
-trong supporters. Probably varying conditions make one 
method preferable over the other in certain instances. But in 
all cases where used as specified, the cure is positive, auto- 
matic, safe and dependable by either method. Furthermore, 
there is no discoloration of the pavement where calcium 
chloride is used. 

Both use- of calcium chloride, either when applied on the 

surface of the concrete or when incorporated in the mix, have 

been proven excellent methods of curing through the stud\ 

onducted by the Highway Research Board and both methods 

approved for use by the U. S. Bureau of Publie Roads. 

The application of calcium chloride on the surface always 

p 1 1 > v i des proper curing; the use of calcium chloride in the mix 

not only insures proper curing, but is of particular advantage 

when earl\ strength concrete is desired, due to its ability to 

(derate the setting of the cement. 

The matter of selecting the proper curing method thus 
becomes a matter of choosing between the surface or admix- 
ture method, according to the convenience of the supervising 




omciai. Either one is a superior curing method, 
-pec I value in cold weather. 



Botl 



i are 



of 




PAGE lO 



HOW TO CURE CONCRET 



SURFACE CURING 



Curing of a concrete >lab by spreading Dowflake calcium 
chloride on the surface is a simple operation. Immediately 
after the wetted burlap has been removed and the pavement wi] 1 
carry the weight of the spreader without detrimental effect to 
the surface, you simply put on a uniform coating of calcium 
chloride with a hand spreader, using not to exceed 2 pound- 
per square yard. 

If thought desirable, the surface of the pavement may be 
broomed or squeegeed as soon as the calcium chloride has 
gone into solution. In this way the calcium chloride solution 
is uniformly and thoroughly distributed over the entire surface 
of the slab. Under no circumstances does curing with Dow- 
flake cause any discoloration of the slab. 

It was recognized in the early days of surface curing with 
Dowflake that it kept the surface wet and performed its curing 
by retaining sufficient moisture to prevent premature drying 
out. It was thought at the time that retaining this surface 
moisture did the whole job. Later study proves, however, that 
while it retains sufficient moisture to complete the hydration of 
the cement, it also penetrates several inches into the pavement 
and has a favorable action in speeding up and completing the 



cure. 



Since the government tests are conclusive and since the 
surface method is approved by the U. S. Bureau of Public 
Roads, the surface treatment has gained popularity. Probably 
its greatest advantage to the paver lies in the fact that it is a 
one man job that leaves visible evidence for accurate and rapid 
inspection. It takes away half the curing troubles and annoy- 
ances. It is fast, safe and certain. 



PAGE T1 



HOW TO CURE CONCRETE 



SURFACE APPLICATION OF DOW FLAKE 

CALCIUM CHLORIDE* 

After the concrete has been properly finished according 
lo specifications of the contract, it should be protected against 
rapid drying by covering with burlap thoroughly wetted as 
soon as, in the judgment of the engineer, the concrete has suf- 
ficiently set to prevent marring the surface. The burlap 
should be kept continuously wet by sprinkling during the day 
as required. 

A- -oon as practicable after the concrete has taken its final 
set, usually on the day following the day of pouring of the 
concrete, all burlap should be removed and the pavement cured 
by means of dry flaked calcium chloride applied to the surlace. 

. The surface should be covered with Hake calcium chlor- 
ide, applied at the rate of not to exceed two (2) pounds per 
square yard spread by means of a squeegee or suitable me- 
chanical spreader so that uniform distribution is obtained. 
Satisfactory application cannot be obtained by spreading with 
shovels and brooms. Should there be any lumps, these should 
be broken or removed from the surface of the pavement. 

The calcium chloride should not be applied during a 
rainfall. If it should rain within a period of two (2) hour- 
following the application, an additional quantity equal to the 
amount lost should be applied. 



n 



-e re 



^commendations are based on A. S. T. M. Designation: C83-31'I 




PAGE 12 



HOW TO CURE CONCRETE 



ADMIXTURE CI KING 



A solution of Dowflake calcium chloride added to the 
mix means that when you mix the cement and pour the slab 
you include the lining agent at the same time. This curing, 
-o far as the contractor i- concerned, is performed and in- 
spected while mixing, leaving no curing trouble for later con- 
sideration. 

Becoming a part of the gauging solution, the curing in- 
gredient permeate> the entire slab, curing uniformly from top 
to bottom. It accelerate- the set, gives high early and perma- 
nent strength-. It lessens the time needed for protection against 
cold, and les-ens also the time form- must be kept in use. It 
work- while men and equipment are employed elsewhere. 




The curing begins as soon as the slab is poured. Exhaust- 
ive tests show such gratifying results that many engineers 
consider this method equal to any form of curing. It is en- 
tirelv automatic and simple. 

J 

The admixture method cures thoroughly, without discolor- 
ation. The surface is smooth and long wearing, the slab a 
satisfaction to contractor and ollicial alike. 



PAGE 13 



HOW TO CURE CONCRETE 




< 



ADMIXTURE APPLICATION AM) APPARATUS* 

Where used a- an admixture, Dowflake calcium chloride 
should always he incorporated in the form of a solution. It is 
simply dissolved in a part of the gauging water. The amount 
of Dowflake required for admixture use i> determined on the 
basis of cement used. This percentage varies from 1%% to 
1', liv weight of cement, according to climatic condition-. 

Admixture Apparatus 

There are many simple forms of mixing apparatus and 
method- oi preparing solution-. A very simple, yet a satis- 
factory alternate method of preparing the solution is to use 
two 60 gallon barrels or drum- mounted on a small platlorm 
built on the >ide of the mixer. First place about 35 gallons oi 
water in the barrel and then pour in two 100-pound >aeks ol 
Dowflake. Mix thi- thoroughly so that all of the Dowflake is 
diV-olved, tlxm fill the barrel with water to the 50 gallon mark. 
From thi- barrel take as many gallons ol solution a> is ncce— 
cary to give the proper percentage. As an example, one gallon 
will contain four pounds of Dowflake. Another barrel may be 
used for mixing the solution while u-ing the first barrel. This 
always gives an additional supply of 50 gallons, so that there 
is no holding up ol the mix in order to have the Dowflake 
-olution read\ . 

Manx pavers today carry admixture apparatus as standard 
equipment. If your mixer- are not thus equipped, you can 
obtain the apparatus from the manufacturer or it can be made 
from blueprints which we will furnish. It consists of tanks 
for mixing the proper solution together with a means of intro- 
ducing the correct amount of solution into each batch along 
with the water. Spe< ifications for admixture curing will be 
iound on page 16 and following pages of this book. 

Method of Introducing Solution into the Mix 

A punitive approved method shall be used for adding the 
calcium chloride -o hit ion to the mix. Am method used -hall 

*TI»e-e recomnn ins are based on A. S. T. M Designation: C82-31T 



PAGE 14. 



HOW TO CURE CONCRET 



be subject to the approval of the engineer. The amount of 
gauging water shall be corrected to allow for the amount of 
calcium chloride solution added. 

Amount. The amount of calcium chloride required shall 
be on the ba>i- of percentage by weight according to the amount 
of Portland cement u-ed. The table below w T ill give the per- 
centage recommended for various climatic conditions, consid- 
ering at the >ame time the typical local cements used. It is not 
necessary that absolute accuracy be maintained; for example, 
for the American size hag of cement two per cent may be fig- 
ured on the basis of two pounds per bag. However, on account 
of the difference between the Canadian and the American bag, 
the columns below will refer to percentages. 

Temperature- averaging about 70° F 1%% 

Temperature- averaging between 70° and 40° F 2% 

Temperatures averaging between 40° and 30° F 3% 

Temperature- below 30 F 4% 

Under no circumstances should more than 4% be used. 




PAGE T 



HOW TO C-^E <ZC P^ETE 




RECOMMENDATIONS WD SPECIFICATIONS FOR 

\I)MI\TIKE CURING 



It has ! :i o |»ri\il< g< to collecl from the recommend- 

5 of j rnmen -t.it.- and other officials, and from inter- 

1 , ,gi, H the data from which to n ommend process 

ml mat •! dmixture curing. Since admixture curing 

t • such an important part <>f concrete work, we 

hav< fell it advisable to dii\ tin- various recommendations 

nth th< aim stablishii _ standard- of practice, materials, 

nd t nul t< indardiz* also methods ol patch- 

insp ondil ns under which materials should l»« 

t tounts to ; . ti i id method of application, and al><> 

td. finite p • ties tnatei - must meet We are, then-lore 
giving ll(»wi _ in tion based on proper \< ommend- 

It.-. i. latio v\ill | maintained up to dab 

g Mmu i < ure ( om ■ "" is published. As turn 

I ,,. m I - • l»< Ik i t practi< • thej v% i 1 1 I>« incoi 

,| in dati< < )m i sou nf inform 

t i the t nost \|»ert* oi the country and thei 

findii with them a d« . oi a uracj which ma) !»• 

i «-l a l>\ the i i ■ ting ei _■ neers. 

I .in :ii n tin- volume i n !■ umm! niIcK 

in i -),. work oi sts li iw* departments, count) 

and . n« a- well .<- in\ other t< linn al n • n 



\N 



ret* -; For J era] \ i the ~|>< 

» which d ii H<»u t<> ( lun I oncreti 

\h I l«\ ma i . throu lout tin* count! J and 

s| II , to |" iheii value in each 

II to Cu ( W int >' 

.(.. ili. i it - n<l m ill be more tl pl< d 

. • - t of th »ugh g la 1 »< • rid field 



MVII l\l. MM II \< VTION 



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HOW TO CURE CONCRETE 



2. Physical Properties. The calcium chloride shall be 
in ihe form of loose, dry flakes, and when lested In means ol 
laboratory -■ teens and sieves shall meet die following require- 
ments: 



Passing % inch screen 100 ' , 

Retained on ^4 inch screen . . . Not more than 20' , 
Passing 20 mesh sieve ....... Not more than 10% 

3. Chemical Composition. The chemical composition 
shall conform to the following requirements: 

CaCl 2 (anhydrous) ..... Not less than 77. 0' 



MgCL Not more than 0.5% 

NaCl Not more than 2.0' J 

Other impurities Not more than 1.0% 

Note — Dowflake more than meets the above A. S. T. M 



specifications. 




s 



4. Packages. The calcium chloride shall be delivered 
in moisture-resisting bags or sacks containing 100 pounds 
each, or in drums. The name of the manufacturer, the batch 
number, and the percentage of calcium chloride guaranteed by 
the manufacturer shall be plainly marked on each container. 

Inspection 

5. The manufacturer shall take and retain representa- 
tive sealed samples from carload lots and hold the same for a 
period of twelve months subject to demand by the purchaser. 
Every facility shall be provided the purchaser should he elect 
to have his own representative sample the material at the plant. 
If the purchaser decides to sample the material after delivery 
in the field, it is understood that a 3 per cent variation in con- 
tent of CaCl 2 from the chemical composition stated in para- 
graph 3 shall be permissible, but this shall not in any way 
relieve the manufacturer if the sealed sample taken at the time 
of manufacture does not show in analysis at least 77 per cent 

CaCl 2 . 

6. Rejection. Calcium chloride shall be rejected if it 
fails to pass any of these specifications and if it cakes or be- 
comes hardened in the containers. 



PAGE 17 



HOW TO CURE CONCRETE 



GENERAL INFORMATION ON DOW KI.AKE CURING 

Corrosion 

Since calcium chloride is a salt, many engineers are of 
the opinion that corrosion of reinforcing steel may result when 
this material is added to a concrete mix. However, the steel is 
not subjected to the effects of calcium chloride in its salt state, 
but to a mass of concrete in which has been included a minute 
amount (.003 of the mass) of a salt that has been neutralized 
by the cement, which is a strong alkaline material. If the 
reinforcing is properly embedded in the concrete it will be 
impossible for corrosion to occur under any conditions. 

Among the researches reported as to the corrosion of 
reinforced steel are those of J. G. Pearson, former physicist 
of the U. S. Bureau of Standards. This investigation revealed 
that corrosion was absent over the greater portion of the sur- 
face of the rods, w hat rust occurred being localized apparently 
where voids occurred on the surface of the steel. It was also 
noted that the corrosion as indicated by the one year and five 
year specimens was not progressive. (A. S. T. M. Vol. 23, 
Part II, page 327). 

In a discussion presented before the American Society 
for Testing Materials, H. S. Mattimore of the Pennsylvania 
Highway Department stated, that upon examination of calcium 
chloride admixture concrete reinforced with cold drawn wire 
mesh there was no evidence as to corrosion of the wire mesh. 
Thi> examination ha^ covered a period of ten years. 

Volume Changes 

Volume changes oi concrete occurring during the setting 
of the cement and due to temperature and moisture changes 
affect definitely the service to be derived from a concrete 
structure. If the stresses set up during these changes exceed 
the strength of the concrete, excessive cracking will result. 
Volume changes may be due to a number of factors, but one 
of the most important is the lo>s of moisture during the setting 
period. Calcium chloride, either applied on the surface or 
incorporated in the mix, controls the moisture loss so that 
volume changes are reduced to a minimum and cracking is 
prevented. 



PAGE IS 



HOW TO CURE CONCRETE 



Does Not Cause Scaling 

During 1929 a survey of the surface condition of approx- 
imately two thousand (2,000) miles of concrete pavements was 
conducted l»y the Curing Committee of the Highway Research 
Board. Of this mileage approximately 1,250 miles was cured 
by the surface application of calcium chloride and 600 with 
the dirt and water method. This survey covered the states of 
Wisconsin, Minnesota, Illinois, Missouri, and Rhode I>land. 
The following conclusions a> to this survey were drawn by the 
Committee: 



(a) Calcium chloride surface application used 
ing method under normal conditions is not a primary 



scaling. 



as a cur- 
cause of 



(b) If conditions conducive to scaling are present the 
M:-ale will probably occur to some extent under either earth and 
water or calcium chloride surface method of curing. 

(c) Insofar as calcium chloride surface curing is con- 
cerned, scaling is not an important factor. 

Workability 

The results of vears of practical experience with Dowflake 
as an admixture for concrete mixes have definitely indicated 
that there is a decided increase in workability. In many cases 
contractors have been more enthusiastic over what they call the 
lubricated mix than they have over the other features of Dow- 
flake, since workability is a great factor in the rapid comple- 
tion of concrete construction or paving work. Dowflake has 
been recommended by many of the contractors who have found 
it unnece»ary to use any other fattening mixture in order to 
maintain the progress with the minimum amount of labor that 
they desired. 




PAGE 19 



HOW TO CURE CONCRETE 




PATCHING CONCRETE PAVEMENTS 

Patching operations on concrete roads are quite often 
necessary because of condition- which cannot always be con- 
trolled. No matter how careful a contractor may be, sagging 
of sub-grade will occur from drainage or unsubstantial fill-. 
Upon occasions, frost action in water pocket- and other cau-es 
will break the pavement, and in other cases severe overloading 
and heavy traffic have freak actions upon parts of the pave- 
ment. While the amount of patching neee--ary is being le— 
tied in almost every new pavement, it is a factor which must 
have consideration. If it must be done at all, it -hould be 
done well. 

When patching operation- arc necessary two important 
factors must be con-idered. The broken -ection mu>t be com- 
pletely removed and the slab broken back to a point where 
-ub-grade and -lab are again perfect. Preparing the pave- 
ment for patching require> the use of a suitable machine for 
breaking out the concrete. When the hole is cleaned out. it 
-hould be filled with concrete to which an admixture of Dow- 
flake ha- been added. It will then obtain sufficient strength to 
permit early use. 

Many territories require the admixture of Dowflake in 
concrete used for patching work, even though they do not 
always i ure their -lab with Dowflake. The rea-ons for this 
are that a pavement i- rarely closed for patching. Barriers are 
set up to close off part of the road and there i- a considerable 
expense and a great deal of trouble involved in maintaining 
hairier- and danger lantern- an-i -ignals. 

Admixture curing for patch work has another great ad- 
vantage in that the Dowflake. through it- property to absorb 
and hold moisture, give- a much better bond to the old part- 
of the pavement and the patch is not likely to break away as 
with the ordinary mix. 



PAGE 2 



HOW TO CURE CONCRETE 



DOWFLAKE FOR COLD WEATHER 

CONSTRUCTION 



The difficulties of cold weather construction have been a 
challenge to engineers and contractors alike. Solving cold 

a wealth 



weather problems has brought to 
ments in concrete construction. 



light 



of improve- 
them, the use of 



^^ Among tnem, trie use 

calcium chloride in cold weather concreting stands out as a 
safeguard not to be neglected. 

Use calcium chloride in all cold weather concrete work. 
Do not expect it to take the place of other necessary factors. 
It will not make a satisfactory concrete from frozen aggre- 
gates — nor ice water. The soundest rules for winter work 
involve these essentials: 1— 



—Aggregates and water must be 
warmed to 70° F. or above, though not too hot. 2 — They 
must be kept warm until satisfactory strength is secured. 
3 — Sufficient moisture must be retained or supplied to continue 
the chemical action. 4 — Low water ratios and richer mixes 
give greater early strength. 

Dowflake calcium chloride, through hundreds of critical 
tests, has shown marked properties for aiding all these four 
factors essential to cold weather work. 

High Early Strength 

Of first importance is the acceleration of the chemical 
action. Dowflake speeds up the setting of cements and the 
attaining of high early strengths. Such concrete has attained 
safe strengths in 30% to 60% less time. In dangerously cold 
weather or exposed locations, the sooner the concrete is safe 
the less danger from sudden and excessive cold and storm. 

Secondly, once a warm mix is placed, chemical action 
itself supplies part of the necessary warmth to complete a 
cure. Dowflake aids this chemical action, causing it to arrive 
at a given strength in about half the time. 

Dowflake aids also in retaining sufficient moisture for 
continued chemical action, preventing to an extent too early 
drying out. 

Use Dowflake in all winter work but use it wisely, not as 
a substitute for heated aggregates — not as a substitute for 



PAGE 21 



HOW TO CURE CONCRETE 



continued warmth and moisture — nut as a substitute for tar- 
paulin or canvas protection — hut as an aid to all these, which 
will, along with such intelligent protection, give you safe con- 
crete in half the time. It puts concrete out of danger in a verv 
short time when rightly used. How important this is will be 
readily understood from the statement in the concrete engin- 
eers hand hook where it is said that concrete at 40 requires 
four times as long a period to ohtain a given strength as the 
same concrete at 50° and ten times as long at 40° as at 70°. 



Concrete making is a 



chemical action 
warmth and moisture. Dow flake is, we firmly 
saiy element, a safeguard in all cold weather 



which requires 
believe, a neces- 

work. 



Experiment- have shown that from two to four per cent 
f Dow flake can be used to decided advantage, depending 
upon the temperature. 




PAGE 22 



HOW TO CURE CONCRETE 



MISCELLANEOUS INFORMATION 



Table for Converting Cubic Yard Weight to Tons 

In view of the fact that all shipments and most purchases of 
coarse and fine aggregates are based on the ton weight, the following 
conversion table worked up by Mr. Theo. A. Polansky, C. E., Parkers- 
burg, W. Va., should prove of general service. 

Table Showing Cubic Yard Weights in Pounds in 

Ton Weight Equivalents 



Weight of 




Fractional 


Weight of 




Fractional 


aggregates in 


Equivalent 


number of 


aggregates in 


Equivalent 


number of 


pounds per 


weight 


cubic yds. 


pounds per 


weight 


cubic yds. 


cubic yard 


in tons 


per ton 


cubic yard 


in tons 


per ton 


2,100 


1.050 


0.952 


2,600 


1.300 


0.769 


2,150 


1.075 


0.930 


2,650 


1.325 


0.754 


2.200 


1.100 


0.909 


2,700 


1.350 


0.740 


2,250 


1.125 


0.888 


2,750 


1.375 


0.727 


2,300 


1.150 


0.869 


2.800 


1.400 


0.714 


2,350 


1.175 


0.851 


2.850 


1.425 


0.701 


2,400 


1.200 


0.833 


2,900 


1.450 


0.689 


2,450 


1.225 


0.816 


2,950 


1.175 


0.677 


2,500 


1.250 


0.800 


3,000 


1.500 


0.666 


2,550 


1.275 


0.784 









Weight of a Cubic Foot of Substance 



Pounds 

Asphaltum 87 

Brick, Best Pressed 150 

Brick, Common Hard 125 

Brick, Soft Inferior 100 

Cement, Portland 1 00 

Clay, in Lump, Loose 63 

Coal, Bituminous, Solid ... 84 
Coal, Bituminous, Broken.. 49 
Earth, Loam, Dry, Loose . . 76 
Earth, Loam, Moderately 
Rammed 95 



Gravel . . 
Ice 

Iron. Cast 
Lead .... 



Pounds 

90-106 
. .. 60 
...450 
...711 



Lime, Loose 53 

Limestone 168 

Sand, Loose 90-106 

Shale 162 

Sandstone 151 

Water 62 ' 



Square Yards Per Mile 



Width 

road in 
10 

12 
14 

16 
18 

20 



of 

feet 



^q. yds. per 
lineal foot 

1.1 

1.3 

1.5 

1.7 
2.0 

2.2 



Sq. yds. 
per mile 

5866 
7040 
8213 
9387 
10560 
11733 



Width of 

road in feet 

24 

28 
30 
32 
36 
40 



Sq. yds. per 
lineal foot 

2.6 
3.1 
3.3 
3.5 
4.0 
4.4 



Sq. yds. 
per mile 

14080 
16427 
17600 
18773 
21120 
23466 



PAGE 23 



HOW XO CURE CONCRETE 



DOWFLAkE SHOULD ALWAYS BE KEPT 

ON HAND 



Dowllake has so many uses that it ought to he on hand 
wherever road materials are stored. Its use as a dust-proofing 
agent has brought about safer driving conditions on thousands 
of miles of gravel roads — has permitted residents along these 
roads to enjoy summer weather free from the annoying, un- 
healthy dust cloud. It has made hundreds of communities 
cleaner, better places in which to live — has brought more busi- 
ness to the merchants of those communities. And it has made 
the road man's job easier by permitting him to gi\e moist, 
firm, dust-free, easily maintained roads at no extra co>t to the 
taxpayer. 

By saving money in concrete curing, keeping roads open 
to traffic in summer and winter, preventing all kinds of material 
from freezing, Dowllake gives a service that makes its use 
almost indispensible to leading highway officials. You will 
find Dow flake included in road construction budgets in many 
states and communities. You should use it in your locality. 




PAGE 3 4 



HOW TO CURE CONCRETE 



I < >li THAWING MANHOLES, SEWERS, HYIHiWTS. 

CULVERTS, ETC. 

Dowflake is a very useful article to have on band in win- 
ter to prevent frozen hydrants, manholes, sewers, culvert-, et< 

Fire hydrants in which the drip valv re |du ;ed, .nnl which 

stand in low, wet ground are likely to become frozen in cold 

weather. A small quantit) oi Dowflake in solution hum will, 

except in the most -even- weather, k i» the hydrant in workin 






ordei throughout the winter. 

For frozen catch basins Dowflake is aim pi) poured directl) 
from the bag into the grating <-r manhole. Within a few min- 
utes the catch lu-in will have become sufficient!) ch n «»l i< 
to permit surface water to move. 

For Keeping III Kinds of Material from Freezing 

The low freezing point of calcium chloride, phi- its ea 
of application and handling, makes it- use valuable as I safi 
guard against the freezing of various types ol construction 
materials, such as -and, gravel, etc. N<> matter what youi cold 
weather construction or stora problem, investi ite Dowflak 
it ma) prove the deterrenl against freezing \<»n are lookin 



if 



lor. 




- A - ~ ? ^ 



HOW TO CURE CONCRETE 



THE FIRM BEHIND THE MANUFACTURE OF 

DOWFLAKE CALCIUM CHLORIDE 



Dowflake is manufactured in one of the largest and mo>t 
modern chemical plants in the world. All of the resources, 
experience and knowledge of thi> vast organization where over 
200 chemical products are manufactured are behind the pro- 
duction of Dowflake. Thousand> of tons of this material are 
produced each year. And each year sees wider distribution. 

The present Dow plant illustrated below covers over 230 
acres and employs 2500 men. There are 310 buildings and 
18 miles of standard gauge railway tracks within the plant. 

Steady, uninterrupted production, plus extreme care in 
manufacturing methods, makes Dowflake calcium chloride a 
dependable, high quality, effective dust prevention and con- 
crete curing agent. 



THE DOW CHKMICAL COMPANY 

M1DLAXD. MICHIGAN 

Branch Sales Offices 

60 Ea^ 12nd Street, New York City 

Second and Madison Streets, Saint Louis 




RACE 26 



HOW TO CUR 



ONCRET 





A propcr/v cured pavement 



PAGE 27 








77-80% 
CIUM CHLORIDE 

HTWUDIIB 17,1925 - JULM?^* 

100 LBS. NET 



I 




MIDLAND. MICHIGAN